Molecular diagnosis of entamoeba species

Publication Type:
Thesis
Issue Date:
2007
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Amebiasis, one of the major intestinal diseases of man, is caused by the protozoan pathogen Entamoeba histolytica. It is the second leading cause of death from parasitic disease worldwide. Although E. histolytica is recognised as a pathogen, the ability of the other Entamoeba species to cause disease is unclear. However, recent studies highlight the recovery of Entamoeba dispar and Entamoeba moshkovskii from patients with gastrointestinal symptoms. Traditionally, E. histolytica was diagnosed by microscopy of stool samples however, with the discovery of two other morphologically similar species (E. dispar and E. moshkovskii), microscopy can no longer be relied upon to diagnose amebiasis. In this study a total of 5921 samples were tested over a period between January 2003- June 2006, which were submitted to the Department of Microbiology at St.Vincent's hospital Sydney, Australia. One hundred and seventy seven samples (2.9%) were microscopically positive for cysts or trophozoites of E complex (E.histolytica, E.dispar, E. moshkovskii), either singly or in combination with other human protozoan parasites. In addition, stool samples collected from patients microscopically negative for parasitic cyst or ova (51) and healthy controls (51) (control group) were also tested. PCR targeting the 18S ribosomal rDNA was performed on stool samples and the amplicons were confirmed using sequencing. The PCR showed a specificity of 100% and a sensitivity of 81%. A prevalence of 5.6 % was observed for E. histolytica and a higher prevalence of E. dispar (70.7%) and E. moshkovskii (61.8%) was found. The patients infected with only E. dispar (5 patients), E. moshkovskii (3 patients) and with a mixture of both (7 patients), and the absence of other protozoan parasites, viral and bacterial pathogens indicate the potential of these organisms in causing diarrhoea and abdominal pain. DNA of E. moshkovskii was not detected in the stool samples collected from the healthy controls (control group). These results further suggest that E. moshkovskii may not simply be a commensal of the human gastrointestinal tract and provides additional evidence for E. moshkovskii as a cause of diarrhea and other gastrointestinal disorders. The findings of this study raises concern that E. moshkovskii could be a potential pathogen thereby suggesting a review of the pathogenic status of this parasite is necessary. Further studies are needed to determine the role of different strains of E. moshkovskii in causing diarrheal diseases in our population.
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